Question

Compare $B-B$ bond length in following molecules.

• A. $x>y$
• B. $y>x$
• C. $x=y$
• D. None of these

Answer 1

Answer: (B)

$y>x$

The bond length $y$ is greater than the bond length $x$. The bond length $y$ is $175$ pm and the bond length $x$ is $172$ pm.

Fluorine is more electronegative than chlorine. Hence, the electrons of $F-B$ bond are more towards $F$ than the electrons of $Cl-B$ bond. Thus, the partial positive charge on $B$ atom is more in fluoro derivative than in chloro derivative.

Hence, the attraction for the bond pair of electrons of $B-B$ bond is greater for the fluoro compound than for chloro compound.

Hence, $y>x$.